En el presente trabajo se dan a conocer los resultados de las observaciones de campo de mamíferos marinos realizado en el segundo semestre del año 2000 en las Islas Galápagos y sus alrededores, durante un crucero oceanográfico del Instituto Oceanográfico de la Armada del Ecuador.A total of 32 species of marine mammals have been recorded waters of the Galapagos Islands (including two species of sea lions and a sigthing of the southamerican sea lion, Otaria flavescens). This paper presents records of marine mammals collected during an oceanographic cruise (B/I ORION-CO-II-2000) around Galapagos Islands. The cruise was carried out between transects 089° W and 092° W from August 1 to August 16 (2000); along 2557 nautical miles. The work also included observations made from eighteen oceanographic stations. A total of 637 individuals and 5 species of marine mammals were recorded. In order of abundance these were: Common dolphins, Delphinus delphis and Pantropical spotted dolphins, Stenella atenuatta (n=400); Galapagos sea lions, Zalophus wollebaeki (n=130); Bottlenose dolphins, Tursiops truncatus (n=106); and Bryde's whales, Balaenoptera edeni (n=1). The relative abundance was 0.25 ind./ nautical mile and the daily abundance was 39,81 ind./ day. Most of the individuals were recorded between 00° 30' N; 92° 00 W (n=203) and 00° 10' S; 91° 34 W (n=204). Individuals were sighted primarily in areas considered to be high productivity such as upwelling areas.